Transmitters are often used in communications, and one important component is the power amplifier (PA). The PA is configured to amplify weak signals without adding distortion. The PA is usually power hungry, typically consuming 30% (or more) of total power. Furthermore, the PA is expensive, usually making up 30% (or more) of the total cost of a transmitter. One characteristic of a power amplifier is that when the input power is relatively small, the output power is also relatively small. In this operating zone, the PA behaves linearly, but the PA is not very efficient. When the input power is relatively high, the output power is also high. In this operating zone, the PA is very efficient, but the PA loses its linearity. Such non-linearity generates undesirable effects in the signal itself as well as in adjacent channels. To correct for these non-linearities, digital pre-distortion (DPD) systems are often used in the signal chain of a transmitter to improve the quality the output signal of the power amplifier in the transmitter.